1. Field of the Invention
The present invention relates to neck joint structures for stringed musical instruments in which necks of stringed musical instruments are fixed to bodies.
2. Background Art
Conventionally, various types of stringed musical instruments such as electric guitars, acoustic guitars, and violins have been equipped with through-neck structures in which bodies and necks are formed using integral wood, set-neck structures in which necks are bonded to bodies by use of an adhesive, and bolt-on structures in which necks are fixed to bodies by use of joint screws such as wood screws and bolts. Among those structures, the bolt-on structure is superior to other structures in terms of manufacturability and manufacturing cost of stringed musical instruments and can be easily handled, compared to other structures, in replacing necks and in adjusting warps of necks since necks are detachably attached to bodies.
For example, FIGS. 3 to 6 of Japanese Utility Model Application Publication No. S63-195378 show a conventional bolt-on structure of a stringed musical instrument in which the base-end portion of a neck is held inside a recess formed on the upper surface of a body, and a joint screw is put into the lower surface of the body toward the base-end portion of the neck in the thickness direction of the body, thus fixing the neck to the body.
For example, FIGS. 1 and 2 of Japanese Utility Model Application Publication No. S63-195378 and FIG. 3 of Japanese Unexamined Patent Application Publication No. 2000-187481 show another conventional bolt-on structure of a stringed musical instrument in which the foregoing joint screw is obliquely put into the distal end of a neck in its longitudinal direction in the thickness direction of a body.
However, since the neck joint structure of a stringed musical instrument disclosed in FIGS. 3 to 6 of Japanese Utility Model Application Publication No. S63-195378 is designed such that the base-end portion of a neck is impressed onto the bottom face of the recess, which is orthogonal to the thickness direction of a body, by the joint screw, no force is exerted to impress the edge face of the base-end portion of a neck onto (the side face of) a body. In other words, no force occurs in impressing the edge face of the base-end portion of a neck onto a body in the longitudinal direction of a neck.
For this reason, even when a vibration occurs in a string of a stringed musical instrument having the above structure, it is difficult for the body and neck to integrally vibrate together irrespective of the vibration of a string, with the result that the vibration of a string may be easily attenuated in comparison with the through-neck structure and set-neck structure, leading to inability to adequately sustain sound. There is another problem such as a reduction of the sound quality and volume.
Since the edge face of the base-end portion of a neck is not depressed in the longitudinal direction of the neck in a stringed musical instrument having the above structure, a gap is formed between the edge face of the base-end portion of the neck and the body, with the result that the neck oscillates about the base-end portion thereof relative to the body in the width direction of the neck (i.e. the direction orthogonal to the thickness direction of the body and the longitudinal direction of the neck). In this case, the direction of the neck relative to the body may be deviated. That is, the direction of a string (i.e. a string-stretching direction) stretched between the distal end of the neck and the body must be deviated from the longitudinal direction of the body and the proper string-stretching direction relative to the body, causing concern that the proper string-stretching state (e.g. a performing ability and a musical interval) may not be maintained.
Since the neck joint structure of a stringed musical instrument as shown in FIGS. 1 and 2 of Japanese Utility Model Application Publication No. S63-195378 and FIG. 3 of Japanese Unexamined Patent Application Publication No. 2000-187481 is designed to use the oblique joint screw, it is capable of moving the base-end portion of the neck relative to the body in both of the thickness direction of the body and the longitudinal direction of the neck.
However, the oblique joint screw is put into the neck at the position departing from the base-end portion of the neck to its distal end, causing concern that the joint strength of the oblique joint screw applied between the body and the neck may decrease. This point will be described in detail. When an external force is applied to raise the neck along the upper surface of the body due to the “leverage effect” about the support point at the base-end portion of the neck, a large force is exerted on the oblique joint screw, which is positioned between the support point at the base-end portion of the neck and the power point at the distal end of the neck, to move in the upper direction and the thickness direction of the body. Even when the joint strength of the joint screw is intensely exerted on the joint screw in the longitudinal direction, the longitudinal direction of the oblique joint screw differs from the direction of the force exerted on the oblique joint screw due to the “leverage effect”, causing concern that the joint strength of the oblique joint screw may decrease. Decreased joint strength of the joint screw may easily attenuate the vibration of a string, leading to inability to adequately sustain sound as described above. In addition, there is another problem such as a reduction of the sound quality and volume. Furthermore, there is concern that the proper string-stretching state may not be maintained.
The external force for raising the neck along the upper surface of the body includes a tensile force caused by a string stretched between the distal end of the neck and the body. Particularly, a bass guitar having a high tensile force of a string increases a force to raise the neck.
In the structure shown in FIG. 3 of Japanese Unexamined Patent Application Publication No. 2000-187481, the contact area between the base-end portion of the neck and the recess of the body is constituted of three faces having different directions. In actuality, it is difficult to simultaneously establish surface contacts on all the three faces with the wood-working precision.